SAP Note 22667 - Discrepancy PIS - vendor/balances/business volumes

Symptom:

The invoice amounts in the Purchasing Information System do not match those from the balance display of the vendor.
(Accounting -> Financial Accounting -> Accounts payable -> Account -> Balances -> Sales/purchases)

Cause and prerequisites

The date of the update is different for these two analyses. In Financial Accounting, the update takes place on the posting date of the invoice, while in the Purchasing Information System, the purchase order date of the delivery schedule is relevant for the update.

Solution
You can create your own information structure which updates the invoice amount to the posting date of the invoice.